Actions for Particle-scale Simulations for Geothermal Energy Applications

Email RIS file
Bookmark
Report an Issue

Particle-scale Simulations for Geothermal Energy Applications

Author
Al Balushi, Faras
Published
[University Park, Pennsylvania] : Pennsylvania State University, 2023.
Physical Description
1 electronic document
Additional Creators
Taleghani, Arash Dahi
Access Online

Availability

I Want It
I Want It

Finding items...

Graduate Program
Restrictions on Access
Restricted (PSU Only).
Summary
Geothermal energy has the potential to develop into a reliable source of clean and renewable energy due to its widespread availability and minimal carbon dioxide emission during electricity generation. Due to the high temperature of such reservoirs, technologies are continuously being developed to reduce the cost of extracting heat and extend the lifetime of the geothermal systems for profitable heat production. One of the main challenges hindering the further development of geothermal systems is the low heat extraction efficiency characterized by low-temperature produced fluids. In enhanced geothermal systems, where fluid injected flows directly through the geothermal formation, thermal breakthrough or "short-circuiting" causes fast cooling of the geothermal formation due to the presence of shortcut paths connecting the injector well to the producer well. Such an occurrence may lead to the temporary shutdown of the geothermal plant, leaving an enormous amount of untapped heat behind. Efforts to tackle this issue have been focused on delaying thermal breakthrough rather than achieving uniform heat sweeping from the geothermal systems. No technologies or methods are currently available to achieve uniform heat extraction from EGS. To fill this gap, we propose a novel concept of temperature-sensitive proppants to achieve self-adjustable fracture conductivity. Through particle-scale numerical simulations, we evaluate the performance of such proppants for different operating conditions and material properties. My numerical results showed that the permeability of such proppants is affected by in-situ conditions, material properties, and geometric properties. The developed model can be utilized to comprehensively understand the performance of such temperature-sensitive proppants at different operating conditions. Field-scale simulations confirmed the feasibility of using the proposed temperature-sensitive proppants in enhancing heat extraction from EGS by ~50% over 50 years of production when the proposed proppants are used compared to typical proppants with no temperature dependency. Alternatively, closed-loop geothermal systems can be considered, where the working fluid is circulated inside the wellbore. The heat exchange efficiency of such systems is typically low, which limits the use of the produced heat for direct heating applications. In this study, we introduce a method of improving heat exchange between the wellbore and the geothermal formation utilizing coated proppants. Based on numerical simulations, the enhancement of proppant thermal conductivity is discussed. Particle-scale analysis showed that coating sand proppants with a thin layer of copper coating may increase its effective thermal conductivity seven times. Increasing proppant particulate coating thickness further increases the effective thermal conductivity by an order of magnitude. In addition, smaller proppants showed higher effective thermal conductivity compared to larger proppants due to the increased contact with the neighboring particles, resulting in lower resistance to heat conduction. Such conductive proppants can enhance heat conduction between the geothermal formation and the wellbore, increasing the heat extraction efficiency of closed-loop geothermal systems. Drilling costs account for the majority of the cost of developing a geothermal system. During drilling, thief zones (permeable zones) may be encountered. Moreover, fractures may be induced due to the high circulating density of the drilling fluid. If such fractures are left unplugged, excessive fluid loss may occur, which may cause well instability issues or may lead to losing the well in extreme cases. Using lost circulation material (LCM) is a cheap and effective way to prevent further drilling fluid loss to the formation. Granular particles are typically used due to their cost and their ability to form a tight and stable seal. Understanding the performance of such particles after bridging is essential to ensure their stability under fluctuating operating conditions. Here, the sealing performance of granular particles after bridging is discussed. Our analysis revealed that the shape of the particles is one of the most influential factors that impact the sensitivity of such particles to closure stress. Furthermore, the sensitivity of the particle pack permeability to friction is influenced by the particle shape. Numerical simulations offer considerable advantages over laboratory experiments, especially for geothermal systems due to the difficulty in accurately reproducing the elevated temperature. In this study, different numerical tools are utilized to model and design particulates that can enhance the heat extraction efficiency of both open- and closed-loop geothermal systems. Using numerical simulations allows easier control of the design parameters as well as operating conditions to avoid repetitive and costly laboratory experiments that may require different samples from different vendors. The numerical workflow used is validated against laboratory experiments and analytical as well as empirical equations.
Other Subject(s)
Genre(s)
Dissertation Note
Ph.D. Pennsylvania State University 2023.
Technical Details
The full text of the dissertation is available as an Adobe Acrobat .pdf file ; Adobe Acrobat Reader required to view the file.
View MARC record | catkey: 43609599